LIQUID HELIUM-FREE SUPERCONDUCTING MAGNETS AND THEIR APPLICATIONS

A new superconducting magnet (4.6 T, 38 mm room temperature bore) whic h consists of a low-T-c Nb3Sn superconducting magnet and high-T-c Bi2S r2Ca2Cu3O10 current leads has been working in vacuum for about 7400 ho urs without trouble. An experiment at a field of 3.7 T, which is gener ated by an operating current of 370 A, has been continuously performed for 1200 hours. The high-T-c current leads have experienced 13 therma l cycles from room temperature to 10 K. It is found that the high-T-c current leads can hold excellent superconducting properties for a long enough time to be practically used. As a next step, an 11 T-52 mm roo m temperature bore, a 6 T-220 mm room temperature bore and a 5 T-phi 5 0 mm X 10 mm room temperature gap liquid helium-free superconducting m agnet are now under construction.